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Glossary

Reamed versus unreamed nailing

In general, reamed nailing allows the use of larger diameter implants and
may therefore provide greater initial stability. Some studies show a tendency
towards less malunion and nonunion when reaming is performed. On the other
hand, fat embolization is a concern and with the solid unreamed nails, the
forces required to achieve nail torsion are higher. Most centers prefer reamed
nailing as the standard procedure.

Important module-wide statement

Where appropriate, a “generic” fracture zone will be illustrated and not
necessarily the specific fracture morphology under consideration. Where the
fracture morphology determines the fixation technique, the specific morphology
will be shown.

A Schanz screw inserted into one of the fragments

Bone hook

Direct reduction with a bone hook may be helpful in securing anatomic
alignment. Careful insertion and manipulation must be performed in order to
minimize soft-tissue trauma and to prevent injury to the femoral artery.

Guide wire insertion

The guide wire is gently slid through the soft tissue into the predrilled
entry portal. Advancement into the proximal main fragment is usually easier
than in antegrade nailing and is performed under image intensifier
guidance.

The guide wire is inserted up to the area of the greater trochanter, where
it should have good purchase to prevent its slipping out during reamer
exchange.

General considerations

The concept of a poller screw is based on the principle that the
malalignment induced by oblique, proximal and distal fractures can be
counteracted by the nail-directing effect of the screw. Therefore, its position
should aim to counteract the displacement of the fracture. Most often it is
therefore placed in the short side in the distal fragment. If there is a wide
canal, two screws can be placed on either side of the nail path.

It is advisable to insert the poller screw prior to reaming in order to
provide adequate contact between the nail and the screw. If the poller screw is
inserted after reaming, the path of the nail is already set and the poller
screw may not work. A small fracture screw or a locking screw can be used as a
poller screw, depending on the local anatomy.

The reaming process in the presence of the poller screw must be performed
very carefully in order not to harm the reamer tip.

The most frequent indication for poller screws is a proximal or distal
oblique fracture which tends to shift when the axial knee blow technique is
used to close any fracture gap, or when the patient is mobilized.

Distal transverse fractures

In general, the poller screw should be located according to the direction of
the initial fracture displacement. Therefore, in a medial displacement, the
fracture will try to displace medially even after the reduction and poller
should be placed lateral to the proposed nail track.

If there is a wide canal or a very unstable situation, blocking screws can
be placed on both sides of the foreseen nail path.

Distal oblique fractures

Midshaft comminuted fractures

Poller screws are used according to the initial displacement and the size of
the canal. In general, midshaft fractures tend to align better than more
proximal or distal fractures and, therefore, the indication for poller screws
is uncommon.

Determine nail length via guide wire

The maximal length of the nail is determined by comparing a second identical
length guide wire to the one that has been inserted. The correct placement of
the guide wire in the proximal canal should be assessed via image intensifier.
Additionally, the second guide wire must be positioned in contact with the
articular surface of the distal femur. This must be verified by image
intensifier as well.

This will yield the length of nail that would reach to the tip of the
greater trochanter – the clinically desirable nail length may be less,
depending on the fracture level and morphology.

Nail diameter

It is important to measure the medullary diameter at the mid portion of the
femur, which represents the narrowest segment of the medullary canal.

The inner cortical edge should touch with the inner numbered disk of the
ruler aperture. In the illustration an inner cortical diameter of 14 mm is
shown.

Consideration for special situations

In multifragmentary fractures, or in open fractures with bone loss, it is
safer to perform preoperative planning on the uninjured leg. In bilateral
femoral fractures, the less comminuted side should be used to determine the
length and diameter of the nail.

Sequential reamer size increase

After the tissue protector has been introduced, the reamer shaft, fitted
with the initial reamer head is inserted over the guide wire. Usually reaming
begins with a 9 mm medullary reamer.

The reaming is performed in sequential steps with increments of 0.5 mm
each.

As soon as chatter from cancellous bone can be felt and heard, the inner
cortex has been reached. This may not be the case in segmental fractures, or
when severe comminution is present.

Reaming must be performed one or two increments beyond the planned nail
diameter in order to allow a smooth nail insertion. For example, for a nail
diameter of 10 mm, drill bits of up to 10.5 or 11 mm diameter are used. If a
very tight fit of the reamer can be felt before the desired reaming size is
reached, one should consider a smaller diameter nail than previously
planned.

Pitfalls: eccentric and overaggressive reaming

Eccentric reamingEccentric reaming can cause weakening of the adjacent cortex which may
interfere with healing or even cause a fatigue fracture.

Trapping of reamer by slow spinningIf the reamer becomes trapped while reaming, it must be gently removed by
the most senior surgeon, because breakage of the reamer tip in this situation
can be a devastating complication.

Heat necrosis by overaggressive reamingOveraggressive reaming should be avoided because it may cause heat necrosis
of the femoral canal. This applies especially for narrow midshaft canals (9 mm
or less in diameter).

Rapid thrusting/systemic fat embolizationCare should be taken to use sharp reamers, to advance the reamers slowly,
and to allow sufficient time between reaming steps in order for the
intramedullary pressure to normalize. Rapid thrusting of the reamer may worsen
the intramedullary pressure increase that is observed during nailing. This
image demonstrates fat extrusion in a human cadaver specimen with a window in
the proximal section.

This may cause pulmonary embolization of medullary fat, which in turn may
lead to pulmonary dysfunction (lower image in the enlarged view shows an
example of fat embolization through the right atrium).

Special situation: conversion from an external fixator to an intramedullary nail

Because the external fixator is still in place, the Schanz screws must be
partially withdrawn to allow the guide wire, the reamers, and later the nail,
to pass through. The external fixator is held in place by monocortical purchase
to assure that the fracture remains stable. The external fixator also acts as a
joystick for the reduction.

General considerations

During insertion of the nail, it is important that the assistant applies
traction to the lower extremity to prevent shortening and/or angulation of the
distal main fragment. In order to prevent this complication, which is very
difficult to correct, repeated image intensifier assessments are required.

The correct nail placement is important in terms of adequate seating in the
distal main fragment. The nail must never be too long and protrude into the
knee joint because of the risk of damage to the articular cartilage of the
patella. If the nail is sunk more than 2 cm deep to the cortex at the entry
point, the placement of the locking screws will be too proximal. Also, it would
be difficult remove the hardware, should this be required at a later stage.

Distal aiming device

After verifying the correct position of the distal end of the nail under the
image intensifier, the distal aiming device may be attached to the insertion
handle.

For correct measurements through the drill sleeve it must be kept at the
bone at all times.

The contralateral thumb can be used to keep the contact.

Screw insertion

The sites of the skin and fascial incisions for the drill bit and the distal
locking screws may be determined after the drill sleeve assembly has been
inserted in the holes of the aiming device. The length of the locking screws is
read from the calibrated drill bit. The correct length is confirmed
antero-posteriorly under the image intensifier. The insertion handle is now
removed.

Drill sleeve to bone contact

The drill sleeve must remain in close contact with the bone at all times
since it is important for the measurement of the locking screws. Close contact
is maintained by pressing on the sleeve with the contralateral thumb.

Verification of locking screw placement

Final x-rays in two planes should be obtained in all cases in order to check
on the exact locking screw placement.

Pitfall: locking screw too long

It is important to remember that the distal femur tapers from the posterior
to the anterior. Therefore, if a straight AP view is obtained, the locking
screws appear to be inside the bone. If they appear to be outside the bone,
they are most likely too long and will invariably cause pain and possibly
heterotopic ossification. In order to assess the exact length of the locking
screws an AP view can be obtained with 30° internal rotation of the lower
extremity.

Matching of the lesser trochanter shape

Cortical step sign and diameter difference sign

Cortical step signThe presence of considerable rotational deformity may be diagnosed by the
difference in thickness of the cortices above and below the fracture zone.

Diameter difference signThe diameter difference sign is of use at levels where the bone cross
section is oval rather than round. In cases of malrotation, the proximal and
distal main fragments will appear to be of different diameters.

Drilling of screw hole

Proximal AP locking has to be performed by the freestyle method. After
verifying the correct position of the distal end of the nail under the image
intensifier, the proximal locking hole must be visualized by image
intensification.

The image intensifier is brought into a strict AP position of 90 degrees.
The distal hole must project a perfect circle and the tip of a scalpel is
projected into the center of the hole.

This guides the stab incision of the skin. The hole is deepened through the
muscle by blunt dissection and the hole is drilled perpendicular to the nail,
using the radiolucent drill, as described in distal locking of antegrade
nailing (
click
here for distal locking of antegrade nailing). This is then followed by
measurement with a depth gauge and insertion of the locking screw. Care should
be taken to prevent an oblique insertion of a locking screw because it can
become trapped between the firm cortical proximal femoral bone and the nail.
Depending on the fracture pattern, either one or two proximal locking screws
are used.

Maintaining lower extremity positionWhile the locking hole is drilled, the assisting surgeon must prevent the
leg from moving in order not to miss the target hole.

Locking screw insertion technique

The length of the locking screw is determined, using the appropriate depth
gauge. Then the locking screw is inserted.

If a radiolucent drive is unavailable, the projection of the tip of the
drill bit should be placed as centered as possible (see illustration). Start
drilling but assess the position of the tip of the drill bit repeatedly, with
the drill temporarily uncoupled.

Pearl: secure screw using a suture

If the contact between the screw driver and the locking screw is lost, the
screw may move within the soft tissue and become extremely hard to capture. To
prevent this time-consuming complication, the locking screw should be lassoed
with a strong absorbable suture.

Second locking screw

The question as to whether a second locking screw should be used must be
decided by the surgeon on a case-to-case basis.

Insertion of the end cap: conventional way

An end cap may be used, depending on the final relationship of the nail end
to the intercondylar notch of the distal femur.

The distance between the distal end of the nail and the articular surface
determines the appropriate length of the end cap, which ranges between zero and
20 mm in 5mm increments. By no means should the end cap be more distal than the
subchondral region.

The end cap is introduced in the conventional way, using a hexagonal
screwdriver.

Note

Retrograde intramedullary femoral nailing violates the knee joint and should only ever be used for specific situations, not for general fixation of lower femoral fractures. It is especially useful for fractures below a hip prosthesis or below a previous femoral nonunion, or ipsilateral femoral neck and shaft fractures. It also allows screening of the gravid uterus whilst nailing lower femoral fractures in pregnancy.